In U.S. Pat. No. 4,040,747 to Donald R. Webster, issued Aug. 9, 1977, there is disclosed a relatively low cost instrument for measuring and analyzing the optical properties of organic materials to determine the percentages of certain constituents of the test materials. This instrument was developed to satisfy a need for a low cost instrument to rapidly determine the moisture, oil and protein content in produce and grain products. In the instrument disclosed in the patent, a source of wide-band infrared light is positioned to illuminate a sample through a filter assembly in which interference filters are arranged in the form of a paddle wheel mounted for rotation about an axis. As the filter wheel rotates, each filter is brought successively into the infrared light beam. As each filter is moved through the light beam by the filter wheel, the angle of incidence of the light beam on the filter changes and this changes the wavelength transmitted through the filter. Moreover, each filter provides a different range of wavelengths. By detecting the amount of reflection at selected specific wavelengths and the relationships of these reflectivities, the oil, protein and water content of the sample can be accurately and quickly determined.
U.S. Ser. No. 45,089, filed June 4, 1979, discloses an instrument of the type disclosed in the Webster patent, but in which the grinding is carried out automatically in the instrument at the time the measurement is made. In the invention disclosed in the application, a grinder is provided on the instrument with a hopper to hold grain and to introduce it into the grinder. A plate blocks the bottom of the hopper from the grinder so that the hopper may be filled with grain prior to a measuring operation. A reflectivity standard is positioned in the path of the infrared rays prior to each measurement to automatically calibrate the instrument. To initiate operation of the instrument, the reflectivity standard is pivoted out of the path of the infrared light. This action automatically energizes the grinder motor. Then, after a two-second delay to permit the grinder motor to get up to speed, grain is permitted to flow from the hopper into the grinder and the ground grain flows into a chute, the bottom of which is arranged to receive the infrared light passing through the filter wheel. The bottom of the chute is closed by an impeller to remove the grain from the chute. After a delay of 5 seconds, sufficient for the chute to fill up, the impeller is rotated to begin to move the grain out of the bottom of the chute. At this time, the instrument begins to make measurements as the grain in the chute moves through the infrared beam. This provides an automatic averaging from the sample being analyzed.